1 /* 2 * XIP kernel .data segment decompressor 3 * 4 * Created by: Nicolas Pitre, August 2017 5 * Copyright: (C) 2017 Linaro Limited 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12 #include <linux/init.h> 13 #include <linux/zutil.h> 14 15 /* for struct inflate_state */ 16 #include "../../../lib/zlib_inflate/inftrees.h" 17 #include "../../../lib/zlib_inflate/inflate.h" 18 #include "../../../lib/zlib_inflate/infutil.h" 19 20 extern char __data_loc[]; 21 extern char _edata_loc[]; 22 extern char _sdata[]; 23 24 /* 25 * This code is called very early during the boot process to decompress 26 * the .data segment stored compressed in ROM. Therefore none of the global 27 * variables are valid yet, hence no kernel services such as memory 28 * allocation is available. Everything must be allocated on the stack and 29 * we must avoid any global data access. We use a temporary stack located 30 * in the .bss area. The linker script makes sure the .bss is big enough 31 * to hold our stack frame plus some room for called functions. 32 * 33 * We mimic the code in lib/decompress_inflate.c to use the smallest work 34 * area possible. And because everything is statically allocated on the 35 * stack then there is no need to clean up before returning. 36 */ 37 38 int __init __inflate_kernel_data(void) 39 { 40 struct z_stream_s stream, *strm = &stream; 41 struct inflate_state state; 42 char *in = __data_loc; 43 int rc; 44 45 /* Check and skip gzip header (assume no filename) */ 46 if (in[0] != 0x1f || in[1] != 0x8b || in[2] != 0x08 || in[3] & ~3) 47 return -1; 48 in += 10; 49 50 strm->workspace = &state; 51 strm->next_in = in; 52 strm->avail_in = _edata_loc - __data_loc; /* upper bound */ 53 strm->next_out = _sdata; 54 strm->avail_out = _edata_loc - __data_loc; 55 zlib_inflateInit2(strm, -MAX_WBITS); 56 WS(strm)->inflate_state.wsize = 0; 57 WS(strm)->inflate_state.window = NULL; 58 rc = zlib_inflate(strm, Z_FINISH); 59 if (rc == Z_OK || rc == Z_STREAM_END) 60 rc = strm->avail_out; /* should be 0 */ 61 return rc; 62 } 63